Where an underground gas service line is installed leading into a building, applicable federal, state and local laws or Codes require that it be encased in a gas-tight conduit or sleeve along that portion of its length which passes through the building foundation wall and ground slab, to where it emerges within the building. An annular space must be provided between the enclosed gas service line and the exterior sleeve to receive and contain any gas which leaks from the service line within this length, thus to prevent gas leakage into the building, or into any space beneath the building. In addition, a vent line must extend from the annular sleeve space to a point above grade and exterior of the building, to permit the gas to escape to the atmosphere where it will not present a hazard.
In the past, the sleeved portion of the gas service line has been pre-fabricated in the form of a rigid, double-wall elbow pipe section having an appropriate vent aperture at least at the upper end, and sometimes also at the lower end of the sleeve, for venting any escaping gas. The required enlarged horizontal opening through the building wall to receive the sleeve at the proper below-grade elevation is usually provided at the time when the wall is poured of concrete. The elbow sleeve is positioned in the wall opening and sealed with the sealing material, whereupon the area is backfilled to the floor elevation. The ground slab is then poured with the elbow sleeve projecting therethrough. In the usual installation, the pipe vent extends horizontally from the vent aperture at the top of the sleeve, passing through a second horizontal opening through the building wall, and any lower vent pipe is located exteriorly of the building, projecting upwardly above grade from the lower vent aperture of the sleeve, which is underground.
When the sleeved elbow must be replaced, it has been necessary to break out a large diameter opening through the concrete ground slab which is the lowermost floor of the building, and to remove a large volume of earthen fill beneath the floor several feet down to the elevation where the sleeve must pass horizontally through the building foundation wall, whereupon the old sleeved elbow may be removed. The replacement elbow is then positioned, the large hole is backfilled, and the large opening in the floor is repaved. In some instances water conduits or drainage pipes may have been installed subsequent to the original gas service, their presence making it even more difficult to install the replacement elbow.
It is intended by the present invention to substantially reduce the size of the break-out hole, and thus the number of man-hours required for the replacement of the referred to sleeved elbow in a gas service line. For example, using the present invention only a one-foot diameter hole through the ground slab is required, as compared with the usual 3'.times.3', or at least 3'.times.11/2' opening necessitated by previous replacement techniques. The amount of fill removal and replacement is commensurately reduced, and the savings in labor amount to about twelve man-hours per replacement. Of course, some of the labor savings result from increased convenience, as compared with conventional methods, as will be seen.